In the field of subsurface wells such as oil and gas wells, various methodologies are already known for sealing the bore of a tubular well assembly, such as that of a Xmas tree. For instance, for sub-sea wells it is known to arrange a tree cap on top of the Xmas tree spool. The tree cap comprises a stinger which is inserted into the bore of the Xmas tree. In some cases, the Xmas tree spool comprises a production bore and a smaller annulus bore. Furthermore, some Xmas trees are used for injection wells to inject fluid into the well bore. The tree cap may then comprise two stingers, of which one is inserted into each of these bores.
It is also known to seal off bores with other bore barrier arrangements, such as plugs, which are provided with locking means. European patent application EP 0687801 describes a wire line plug with a metal-to-metal sealing, arranged to be locked in a bore with internal locking grooves. The plug has locking keys (4) arranged to engage with the locking grooves of the bore. An axially movable expander sleeve (3) provides radial movement of the locking keys when it is moved axially. The expander sleeve and the locking keys are provided with sliding faces of different inclination, providing different radial moving distances with respect to the axial moving distance of the expander sleeve, in dependence on the engaged inclined face.
In order to lock the stinger or cap in place, it is known to arrange radially movable dogs, which can engage with inner locking profiles in a bore. To move the dogs radially, it is known to slide a locking sleeve along their inner faces. The locking sleeve typically has an inclined face which moves the dogs radially outward when the sleeve is moved down. In order to move such a locking sleeve down, however, it is common to use a tool which, before moving the sleeve, has to be secured to the well arrangement. This is to prevent the tool from moving upward when forcing the locking sleeve down.
The movement of a locking sleeve is typically provided for by hydraulic pistons in the running tool or by providing linear movement with an ROV actuation device.
In the known technologies relating to sealing of bores, seal holder is generally provided for retaining sealing means to effectively seal the bore. Of course, effective sealing is achieved by such sealing means, in combination with the other components, some of which are as described hereinabove.
In prior art, common in the field of sealing bores, seal holders are known to carry sealing elements to form the final seal. However, the focus in such prior art has been found to be not on the seal carrier which merely functions in a normal and known way to form a seal, by virtue of the sealing elements it carries. Rather, the focus has always been on the constructional features of the combination of different components, to form an effective capping. For example, GB 2456191 A discloses a subsea well production tree having an annular cavity, a communication gallery and a tree cap. The annular cavity is located at the upper end surrounding the upper ends of the production bore and annulus bore. The communication gallery is located between the annulus bore and annular cavity. The tree cap has a production bore mandrel and an annular sealing member. The production bore mandrel extends from the upper portion of the tree cap down to the production bore. The sealing member extends from the upper portion of the tree cap down to the annular cavity. The method of sealing comprises landing the tree cap on the tree, inserting the production bore mandrel into the production bore and inserting the sealing member into the annular cavity to form a seal between the communication gallery and annular cavity.
In GB 2456191A again, the focus of the invention is not on any special configuration of any seal carrier/holder. Rather, focus is on a combination of several components such as annular cavity, communication gallery, production mandrel and a sealing member. It is mainly this combination which causes effective sealing and there is no teaching regarding any seal holder/carrier having inherent adaptations for enhancing the sealing action.
From U.S. Pat. No. 5,992,526A it is known a seal holder for use in a tree cap. The seal holder comprises two stab members sealing the bores. The stab members having sealing elements which seal against the bores.
US2009/0151958 A1 describes a temporary sealing element for use in a well, comprising a crushable sealing element which is convex shaped against the pressure side.
Also U.S. Pat. No. 5,685,372 describes a crushable plug for use in a well where the plug has a convex form.
Hence, in existing prior art no teaching exists regarding a seal holder per se, which by virtue of its adaptations, enhances the sealing action of a bore of a tubular well assembly. Accordingly there was a need to design a seal holder, which by virtue of its construction, effectively enhances the sealing of a bore of a tubular well element.